In general resonators, such as a piezoelectric vibrators, are used as a device for achieving a timer function in an electronic apparatus. With miniaturization of electronic apparatuses, a resonator is also required to be miniaturized, and a resonator manufactured using MEMS (Micro Electro Mechanical Systems) technology (hereinafter, also referred to as “MEMS vibrator”) has attracted attention.
In the MEMS vibrator, variations in resonant frequency may occur due to manufacturing variations in some cases. Therefore, the frequency is adjusted by an additional etching or the like during or after the manufacturing of the MEMS vibrator.
For example, Patent Document 1 (identified below) discloses a configuration in which, in a vibrator having a plurality of vibration arms, a resonant frequency is adjusted by respectively reducing a mass portion for coarse adjustment provided at a tip end side of the vibration arm and a mass portion for fine adjustment provided at a base end side of the vibration arm.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-065293.
The mass portion described in Patent Document 1 includes an insulator layer and a conductive layer formed on the insulator layer. In the MEMS vibrator, in the case where such a mass portion is formed and the resonant frequency is adjusted using an ion beam, a pyroelectric material, or the like, the insulator layer may be charged. When the MEMS vibrator vibrates in a state in which the insulator layer on the MEMS vibrator is charged, Coulomb force is generated by the electric charge on the insulator layer so that the resonant frequency fluctuates.